Coupling for drop box system

ABSTRACT

The coupling of the present invention is comprised of a carriage which moves along a track mounted in a support frame by means of a motor driven endless chain. The chain is connected to a pivot plate, which is rotatably attached to the carriage. The chain is connected to the side of the pivot plate facing the drop box, which is to be picked up by the device, at a location below the axis which the pivot plate rotates about, and to the other side of the pivot plate above this axis. Thus when the pivot plate strikes a stop, located near the bottom of the support frame, the pivot plate is rotated such that the tip of a U-shaped bail located on its top surface is raised. As a result the frame can then be moved toward the drop box until the bail is above a hook located on its front end. When the chain then is moved in the opposite direction and the carriage pulled free of the stop, the pivot plate rotates back to its original position and the tip of the bail drops over the hook and engages it.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a coupling for connecting a drop box having ahook located at its front end to the endless chain of a roll off hoist.

There currently are two general systems for loading drop boxes onto atruck for transportation and then unloading them again upon arrival atthe intended destination. One of these systems uses a cable having aloop at its end which fits over a hook located at the front of the dropbox. The cable is wound onto a winch to pull the drop box up a tiltingframe located on the truck. With this system the drop box is unloaded bybacking the truck toward the intended drop point and stopping itabruptly. Inertia then causes the drop box to slide off of the truck.

A more recent system improves upon the winch feed system by providing anendless chain in the tilting frame which can be moved in eitherdirection. A carriage, which is connected to the chain, rides on a tracklocated on the frame. The carriage has a hook located on it which isarranged to engage a horizontal bar located on a tongue at the front ofthe drop box. With this system the carriage can be coupled to the dropbox automatically by running the carriage to the bottom of the frame,backing the truck towards the bin so that it is adjacent to the tongueand then moving the carriage back up the track.

Not only can the drop box be coupled to the lifting device automaticallywith this system, but the chain can be used to positively push the dropbox off the truck when it is time to unload it. This allows more preciseplacement of the drop box and even allows unloading the drop box onto adock having the same height as the truck.

Because the endless chain system is superior to the cable system, manyusers of the latter are changing to the former. However, heretoforedoing so required conversion of each drop box from one having a hook toone having a horizontal bar which can be engaged by the hook on thechain. Otherwise, it would be necessary to manually interconnect thehook on the chain with the hook on the drop box, with a short piece ofcable for example. Conversion is expensive, particularly when a largenumber of drop boxes are involved and manually coupling is inefficient.What is needed, therefore, is a coupling device on an endless chain typeof roll off hoist which automatically will engage the hook of a cabletype drop box.

This is accomplished in the present invention by providing a pivot platewhich is rotatably mounted on the carriage and which is attached to thechain. The chain is connected to the side of the pivot plate which facesthe extremity of the frame at a location below the axis that the pivotplate connects to the carriage and to the other side of the pivot plateat a location above this axis. Mounted on top of the pivot plate is aU-shaped bail which is arranged to engage the hook on the bin. A stop,which is located on the track which the carriage runs on, prevents thecarriage from moving past a certain point toward the extremity of theframe. Thus, when the carriage contacts the stop further movement of thechain toward the extremity causes the pivot plate, and thus the bail, torotate upwardly. When the direction of the motor is reversed, the pivotplate and bail then drop back to their original positions.

In operation, a bin is loaded by tilting the frame from its horizontaltraveling position to an angled position where its extremity isproximate the ground. The carriage then is driven up against the stopthereby raising the tip of the bail. When the bail is lifted the truckis backed toward the drop box until the bail is located over the hookand the carriage is moved back up the track. As the carriage pulls awayfrom the stop the bail drops over the hook and engages it. Furthermovement of the carriage causes the drop box to be pulled up onto theframe and the frame is then rotated to its horizontal position. Inunloading the drop box the chain merely is moved towards the extremityof the frame. A pusher plate located on the carriage contacts the dropbox and pushes it off of the truck.

Accordingly, it is a principal object of the present invention toprovide a coupling for interconnecting a drop box having a loading hookto the carriage of an endless chain roll off hoist.

It is a further object of the present invention to provide such acoupling which engages the hook automatically upon movement of thecarriage along the frame which supports it.

The foregoing and other objectives, features and advantages of thepresent invention will be more readily understood upon consideration ofthe following detailed description of the invention taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a drop box coupling embodying thefeatures of the present invention.

FIG. 2 is an end elevation view of the coupling of FIG. 1.

FIGS. 3 and 4 are side elevation views, at reduced scale, showing thesequence of operation of the device.

PREFERRED EMBODIMENT OF THE INVENTION

Referring to FIGS. 1 and 2 of the drawings, the coupling of the presentinvention comprises a carriage 10 which travels along an I-shaped track12. The carriage comprises a rectangular top element 14 which isattached to paired spaced-apart side elements 16 by a plurality of bolts18. Wheels 20, which are rotatably attached to each side element, fitinside the cavities on the sides of the track to secure the carriage toit.

The track is mounted on a frame 22 which is mounted on a truck (notshown) having a tilt mechanism (not shown) which allows the frame to berotated between the angled loading position shown in the drawings and ahorizontal travel position. A wheel 24 located at the extremity of theframe engages the ground when the frame is in its tilted position tofacilitate fore and aft movement of the truck.

Mounted on the top element 14 of the carriage, by means such as welding,is a pair of side-by-side supports 26. Rotatably mounted between thesupports, by means of a bolt 28, is a pivot plate 30. An endless linkchain 32, which travels in a circular path around sprockets (not shown).Each end of the frame is broken and the two ends are attached to thepivot plate. Thus, as the chain is moved, by means of a motor (notshown) which drives the upper sprocket, the carriage travels along thetrack 10.

Mounted on the pivot plate is a U-shaped bail 34 which extends towardsthe extremity of the frame which is lowered. The tip of the bail extendspast the extremity of the supports 26. A bushing (not shown) which isattached to the top of the pivot plate, receives a bolt 36 which passesthrough openings in the ends of the bail. Thus the bail rotates freelywith respect to the pivot plate. The bail is tied to the pivot plate bymeans of a spring 38 which permits the bail to move relative to thepivot plate but normally locates it in a particular position relative tothe pivot plate.

Located at the lower extremity of the track 12 is a stop 40 whichengages the carriage 10 and prevents it from moving past a certain pointtoward the extremity of the track. The end of the chain 32 which extendstoward the lower extremity of the track is attached to the pivot plateat a point which is below the bolt 28, and the other end of the chain isattached to the pivot plate at a point which is above the bolt 28. Thus,if the motor continues to drive the chain toward the lower extremity ofthe frame after the carriage has engaged the stop 40, the pivot platerotates to raise the extremity of the bail above its normal position.When the motor then is reversed and the carriage is pulled away from thestop 40, the pivot plate rotates in the opposite direction and theextremity of the bail is dropped to its original position.

In operation, a drop box 42 is loaded onto the frame 22 by firstrotating the frame to the angled position shown in the drawings with aspace between the extremity of the frame and the front of the drop box,the phantom line position in FIG. 3. The carriage 10 then is driven downthe track 12 until it strikes the stop 40 and the bail 34 is raised. Thetruck then is backed towards the drop box until the bail is located overthe hook 44 located on the front of the skids 46 located at the bottomof the drop box, the solid line position in FIG. 3. The carriage then ismoved back up the frame which first causes the bail to be lowered overthe hook 44, and then brings the bail into engagement with the hook,FIG. 4. Further movement of the carriage up the frame causes the dropbox to be pulled up onto the frame with the skids 46 sliding along theframe. When the drop box is pulled completely onto the frame the frameis rotated back to its horizontal position and the drop box can betransported by the truck.

To unload the drop box the carriage is moved towards the extremity ofthe frame and the pusher nose 48 located at the front of the supports 26contacts the front of the drop box and the carriage pushes the drop boxback off of the frame 22. Since the drop box is positively pushed off ofthe frame, rather than relying on inertia, it can be unloaded withoutthe necessity of rotating the frame to an angled position. This allowsthe drop box to be unloaded onto a raised loading dock which is at thesame level as the truck.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

What is claimed is:
 1. A drop box loading system comprising:(a) a dropbox having a hook at its front end which can be engaged only from above;(b) an elongate hoist frame having an upper portion with a track definedtherein; (c) an endless chain which is rotatably mounted on said frame;(d) means for moving said chain in either direction along the elongateaxis of said frame; (e) a carriage which is attached to said chain; (f)said carriage including means for moving it along said track as saidchain is moved; (g) a bail attached to said carriage, having a tip whichextends toward one extremity of said frame; (h) a stop, located on saidframe, which prevents movement of said carriage past a certain pointtowards one extremity of said frame; and (i) said carriage includinglifting means for raising said tip above said hook whenever said chaincontinues to urge said carriage towards said one extremity of said frameafter said carriage has engaged said stop and for lowering said tip intosaid hook when said carriage is pulled free from said stop, wherein saidlifting means comprises:(i) a pivot plate which is rotatably attached tosaid carriage about a first axis; (ii) means for attaching the portionof said chain which extends toward one extremity of the frame to saidpivot plate at a location above said first axis, and for attaching theportion of said chain which extends in the other direction to said pivotplate at a location below said first axis; (iii) wherein said bail isattached to said pivot plate.
 2. The loading system of claim 1 whereinsaid carriage comprises paired, upright supports which are spaced apartby a distance which is slightly greater than the thickness of said pivotplate.
 3. The loading system of claim 1 wherein said bail is rotatablerelatively to said carriage, including means for positioning said bailapproximately parallel with said track, when it is not raised, butpermitting it to be moved upwardly or downwardly therefrom.
 4. Theloading system of claim 3 wherein said means for positioning comprises aspring which extends between said bail and said pivot plate.